Poly(ε-caprolactone-<i>co</i>-ε-decalactone)/carbon black or carbon nanofiber composites. Synthesis, morphological, and thermal/electrical properties

Much of the research on biodegradable polymers is currently aimed at developing alternative materials to fossil fuel plastics. Among the biodegradable polymers, the bio-based aliphatic polyesters (<i>e.g.</i> poly-ε-caprolactone, PCL) have had important success in replacing single-use plastics as well as durable consumer goods, mainly in the packaging and biomedical sectors. In other sectors, like electronics, the use of bio-based plastics has received little attention, despite e-waste (pollutant and difficult to handle) being the fastest growing solid waste stream in the world. In this work, P(CL-DL)/carbon black and P(CL-DL)/carbon nanofiber composites with enhanced thermal and electrical properties were prepared and studied. P(CL-DL) copolymers were synthesized <i>via</i> ring opening polymerization (ROP) at CL/DL molar compositions of 95/5, 90/10, 80/20, and 70/30. Their number-average molecular weight (<i>M̄</i> _n) and dispersity index (<i>Đ</i>) lie between 17.5 and 21.8 kDa, and 1.72 and 1.99, respectively. They are thermally stable to up to 300 °C, and show a melting temperature (<i>T</i> _m) and a crystalline degree (<i>X</i> _c) that decrease with increasing contents of DL in the polymer chains. The thermal (<i>k</i>) and electrical (<i>σ</i>) conductivities of copolymers were enhanced by adding, through melt blending, carbon black (CB) or carbon nanofibers (CNF) at 1.25, 2.5, and 5.0 wt%, reaching a maximum value of 0.55 W m^-1 K^-1 and 10^-7 S cm^-1, respectively. The frequency-dependence of the dielectric constant (<i>ε</i>') and dielectric losses (tan <i>δ</i>) was also measured. Two of the composites showed a marked increase of <i>ε</i>' near percolation whereas their tan <i>δ</i> remained low. The thermal and electrical conductivity performances, as well as the increment found in <i>ε</i>' near percolation, are discussed in terms morphology changes produced by variations in both the DL mol% and the nanoparticles wt%. Finally, biodegradable composites with heat and electron dissipative capacities are materials that can contribute to alleviating the problem of e-waste.